Hyperthermia treatment and probe therefor

ABSTRACT

An MRI guided surgical apparatus includes a heat source formed by a laser and an optical fiber carrying the heat energy into a part to be coagulated by hyperthermia with an end reflector to direct the energy in a beam to one side of the fiber end. A reinforcing sleeve for the fiber is mounted in a shielded, Piezo-electric motor which causes movement of the fiber longitudinally and angularly within a rigid elongate cannula. A magnetic resonance imaging system is arranged to generate a series of output signals over a period of time representative of temperature in the part as the temperature of the part changes during that time. The heat source is controlled in heat energy applied and location and orientation of the beam to stop heating when the temperature at the boundary of a tumor reaches the required hyperthermic temperature. Cooling of the tip portion of the probe is effected by expansion of a supplied cooling fluid in gaseous form through a restrictive orifice into an expansion zone at the probe end. The fiber is thus encased in a stiff tubular titanium probe with a relatively small fluid supply duct along the inside of the probe with the interior of the probe acting as a return duct for the expanded gas. Thus the fiber end is contained in gas rather than liquid and the temperature of the probe end can be monitored by a sensor in the probe end and controlled by controlling the pressure in the supplied cooling fluid. The probe is driven in the longitudinal and rotational directions to move the fiber tip.

[0001] This application in a continuation-in-part application from PCTApplication CA01/00905 filed Jun. 15, 2001.

[0002] This invention relates to a method and apparatus for hyperthermiatreatment in a patient.

BACKGROUND OF THE INVENTION

[0003] The treatment of tumours by hyperthermia is known. Thus tumoursand other lesions to be treated can in one known process be heated abovea predetermined temperature of the order of 55° C. so as to coagulatethe portion of tissue heated. The temperature range is preferably of theorder of 55 to 65° C. and does not reach temperatures which can causecarbonization or ablation of the tissue.

[0004] One technique for effecting the heating is to insert into thelesion concerned an optical fiber which has at its inserted end anelement which redirects laser light from an exterior source in adirection generally at right angles to the length of the fiber. Theenergy from the laser thus extends into the tissue surrounding the endor tip and effects heating. The energy is directed in a beam confined toa relatively shallow angle so that, as the fiber is rotated, the beamalso rotates around the axis of the fiber to effect heating of differentparts of the lesion at positions around the fiber. The fiber can thus bemoved longitudinally and rotated to effect heating of the lesion overthe full volume of the lesion with the intention of heating the lesionto the required temperature without significantly affecting tissuesurrounding the lesion.

[0005] At this time the fiber is controlled and manipulated by a surgeonwith little or no guidance apart from the knowledge of the surgeon ofthe anatomy of the patient and the location of the lesion. It isdifficult therefore for the surgeon to effect a controlled heating whichheats all of the lesion while minimizing damage to surrounding tissue.

[0006] It is of course well known that the location of tumours and otherlesions to be excised can be determined by imaging using a magneticresonance imaging system. The imaging system thus generates for thesurgeon a location of the lesion to be excised but there is no systemavailable which allows the surgeon to use the imaging system to controlthe heating effect. In most cases it is necessary to remove the patientfrom the imaging system before the treatment commences and that movementtogether with the partial excision or coagulation of some of the tissuecan significantly change the location of the lesion to be excised thuseliminating any possibility for controlled accuracy.

[0007] It is also known that magnetic resonance imaging systems can beused by modification of the imaging sequences to determine thetemperature of tissue within the image and to determine changes in thattemperature over time.

[0008] U.S. Pat. No. 4,914,608 (LeBiahan) assigned to U.S. Department ofHealth and Human Services issued Apr. 3, 1990 discloses a method fordetermining temperature in tissue.

[0009] U.S. Pat. No. 5,284,144 (Delannoy) also assigned to U.S.Department of Health and Human Services and issued Feb. 8, 1994discloses an apparatus for hyperthermia treatment of cancer in which anexternal non-invasive heating system is mounted within the coil of amagnetic resonance imaging system. The disclosure is speculative andrelates to initial experimentation concerning the viability of MRImeasurement of temperature in conjunction with an external heatingsystem. The disclosure of the patent has not led to a commerciallyviable hyperthermic treatment system.

[0010] U.S. Pat. Nos. 5,368,031 and 5,291,890 assigned to GeneralElectric relate to an MRI controlled heating system in which a pointsource of heat generates a predetermined heat distribution which is thenmonitored to ensure that the actual heat distribution follows thepredicted heat distribution to obtain an overall heating of the area tobe heated. Again this patented arrangement has not led to a commerciallyviable hyperthermia surgical system.

[0011] An earlier U.S. Pat. No. 4,671,254 (Fair) assigned to MemorialHospital for Cancer and Allied Diseases and issued Jun. 9, 1987discloses a method for a non surgical treatment of tumours in which thetumour is subjected to shock waves. This does not use a monitoringsystem to monitor and control the effect.

[0012] U.S. Pat. No. 5,823,941 (Shaunnessey) not assigned issued Oct.20, 1998 discloses a specially modified endoscope which designed tosupport an optical fiber which emits light energy and is movedlongitudinally and rotates angularly about its axis to direct theenergy. The device is used for excising tumors and the energy isarranged to be sufficient to effect vaporization of the tissue to beexcised with the gas thus formed being removed by suction through theendoscope. An image of the tumor is obtained by MRI and this is used toprogram a path of movement of the fiber to be taken during theoperation. There is no feedback during the procedure to control themovement and the operation is wholly dependent upon the initialanalysis. This arrangement has not achieved commercial or medicalsuccess.

[0013] U.S. Pat. No. 5,454,807 (Lennox) assigned to Boston ScientificCorporation issued Oct. 3, 1995 discloses a device for use inirradiating a tumor with light energy from an optical fiber in which inconjunction with a cooling fluid which is supplied through a conduitwith the fiber to apply surface cooling and prevent surface damage whileallowing increased levels of energy to be applied to deeper tissues.This arrangement however provides no feedback control of the heatingeffect.

[0014] U.S. Pat. No. 5,785,704 (Bille) assigned to MRC Systems GmbHissued Jul. 28, 1996 discloses a particular arrangement of laser beamand lens for use in irradiation of brain tumors but does not disclosemethods of feedback control of the energy. This arrangement uses highspeed pulsed laser energy for a photo-disruption effect.

[0015] Kahn et al in Journal of Computer Assisted Tomography18(4):519-532 July/August 1994 and in Journal of Magnetic ResonanceImaging JMRI 1998; 8: 160-164 Vogl et al in Radiology 1998; 209: 381-385all disclose a method of application of heat energy from a laser througha fiber to a tumor where the temperature at the periphery of the tumoris monitored during the application of the energy by MRI. However noneof these papers describes an arrangement in which the energy iscontrolled by feedback from the monitoring arrangement. The paper ofVogl also discloses a cooling system supplied commercially by Somatex ofBerlin Germany for cooling the tissues at the probe end. The system isformed by an inner tube through which the fiber passes mounted within anouter tube arrangement in which cooling fluid is passed between the twotubes and inside the inner tube in a continuous stream.

SUMMARY OF THE INVENTION

[0016] It is one object of the present invention, therefore, to providean improved method and apparatus for effecting treatment of a patient byhyperthermia.

[0017] According to a first aspect of the invention there is provided amethod for effecting treatment in a patient comprising:

[0018] identifying a volume in the patient the whole of which volume isto be heated to a required temperature, the volume being defined by aperipheral surface of the volume;

[0019] providing a heat source and applying heat to the volume withinthe patient by;

[0020] providing the heat source on an invasive probe having alongitudinal axis and an end;

[0021] inserting the end of the probe into the volume;

[0022] arranging the probe to cause directing of heat from the end in adirection at an angle to the longitudinal axis such that a heatingeffect of the probe lies in a disk surrounding the axis;

[0023] arranging the direction of the heat so as to define a heatingzone which forms a limited angular orientation of heating within thedisk such that, as the probe is rotated, the probe causes heating ofdifferent angular segments of the volume within the disk;

[0024] with the probe at a fixed axial position, rotating the probeabout the axis so that the heating zone lies in a selected segment;

[0025] wherein the application of heat by the probe to the selectedsegment causes heat to be transferred from the segment into parts of thevolume outside the segment surrounding the end of the probe;

[0026] and applying cooling to the end of the probe so as to extractheat from the parts surrounding the probe by conduction of heattherefrom.

[0027] Preferably the amount of cooling to the probe is arrangedrelative to the heating such that the parts of the volume surroundingthe end of the probe are cooled sufficiently to cause a net heatingeffect by which substantially only the segment of the heating zone isheated to the required temperature and the parts outside the segment arenot heated to the required temperature. This is preferably arranged sothat the cooling maintains the parts outside the segment below atemperature sufficient to cause coagulation of the tissues therein. Thuswhen the probe is rotated to take up a new angle within a new segment,the tissue in the new segment is not in a condition by pre-heating whichwould interfere with the transmission and diffusion of the heat to thatsegment.

[0028] The arrangement of the present invention, that is the methoddefined above or the method or probe defined hereinafter, can be used ona rigid probe which is intended to be inserted in a straight line into aspecific location in the body of the patient, or can be used on aflexible probe which can be guided in movement through a part of thebody such as a vein or artery to a required location.

[0029] While the most likely and currently most suitable energy sourceis that of laser light, the arrangements described and defined hereincan also be used with other energy sources of the type which can bedirected to one side of the channel through which they are supplied suchas electron beams or ultrasound generators.

[0030] In one preferred arrangement, the above method can be used withMRI real time control of the surgery by which a non-invasive detectionsystem, such as MRI, is operated to generate a series of output signalsover a period of time representative of temperature in the patient asthe temperature of the patient changes during that time. The outputsignals are used to monitor at least one temperature of the volume asthe temperature changes over the period of time. The application of heatto the probe is then controlled in response to the changes intemperature wherein the temperature at the peripheral surface of thevolume is monitored and a measure of the temperature at a location onthe peripheral surface of the volume is used as the determining factoras to when to halt heating by the probe to the location. However thecooling effect can be used without the MRI monitoring to provide anenhanced system in which the whole of the volume required can be heatedto the required temperature.

[0031] In the method in which temperature is monitored, thedetermination as to when to halt heating by the probe to the location ismade based upon the temperature at the peripheral surface of the volume,with the exception that temperatures within the volume may be monitoredto ensure that no serious or dangerous over-temperature occurs withinthe volume due to unexpected or unusual conditions. Thus any suchover-temperature may be detected and used to halt further treatment orto trigger an alarm to the doctor for analysis of the conditions to beundertaken.

[0032] When used as a rigid probe for treatment within a body part suchas the brain or liver, the probe itself may be sufficiently rigid andstrong to accommodate the forces involved or there may be provided acannula through which the probe is inserted, the cannula having an endwhich is moved to a position immediately adjacent but outside the volumeand the probe having a rigid end portion projecting from the end of thecannula into the volume.

[0033] In the preferred arrangement, the heat source comprises a laser,an optical fiber for communicating light from the laser and a lightdirecting element at an end of the fiber for directing the light fromthe laser to the predetermined direction relative to the fiber formingthe limited angular orientation within the disk.

[0034] In accordance with a particularly preferred arrangement whichprovides the necessary level of cooling in a readily controllableprocess, the end of the probe is cooled by:

[0035] providing on the probe a supply duct for a cooling fluidextending from a supply to the end of the probe;

[0036] providing an expansion zone of reduced pressure at the end of theprobe so as to cause the cooling fluid to expand as a gas thusgenerating a cooling effect;

[0037] and providing on the probe a return duct for return of theexpanded gas from the end of the probe.

[0038] In this arrangement, the return duct is preferably of largercross-sectional area than the supply duct and the supply duct includes arestricting orifice at its end where the return duct is larger incross-sectional area by a factor of the order of 200 times larger thanthe orifice of the supply duct.

[0039] Preferably where the probe comprises a tube the supply duct isarranged inside the tube and the return duct is defined by an insidesurface of the tube.

[0040] In this arrangement, the supply duct is attached as tube to aninside surface of the tube and the fiber itself is attached also to theinside.

[0041] In this arrangement, the orifice is provided by a restrictingvalve or neck in the supply duct immediately upstream of the expansionchamber at the end of the probe.

[0042] Where the fiber has a chamfered end of the fiber it may include areflecting coating thereon for directing the light energy to the side.The arrangement of the chamfered end can have the advantage or featurethat the chamfered end is located in the gas rather than being wetted bycooling fluid which can, when there is no coating, interfere with thereflective properties of the coating and thus with the proper controland direction of the light.

[0043] In this arrangement, the chamfered end can be arranged directlyat 45 degrees to provide a light direction lying wholly in a radialplane at right angles to the axis of the fiber. The chamfered end maycarry a coating arranged to reflect light at two different wavelengths.

[0044] In order to accurately control the cooling effect to maintain thenet heating required, there is preferably provided a temperature sensorat the end of the probe, which may be located inside the tube with theconnection therefor passing through the probe to the control systemoutside the probe.

[0045] Preferably the temperature at the end of the probe is controlledby varying the pressure in the fluid as supplied through the supplyduct. This system can allow the temperature to be maintained betweenabout zero and minus 20 degrees Celsius which provides the requiredlevel of cooling to the probe for the net heating effect.

[0046] According to a second aspect of the invention there is provided amethod for effecting treatment in a patient comprising:

[0047] identifying a volume in the patient to be heated to a requiredtemperature;

[0048] providing a heat source for applying heat to the volume withinthe patient,

[0049] providing a probe mounting the heat source allowing invasiveinsertion of an end of the probe into the patient,

[0050] providing a position control system for moving the end of theprobe to a required position within the patient;

[0051] inserting the end of the probe into the volume;

[0052] providing on the probe a supply duct for a cooling fluidextending from a supply to the end of the probe;

[0053] providing an expansion zone of reduced pressure at the end of theprobe so as to cause the cooling fluid to expand as a gas thusgenerating a cooling effect;

[0054] and providing on the probe a return duct for return of theexpanded gas from the end of the probe.

[0055] According to a third aspect of the invention there is provided aprobe for use in effecting treatment in a patient comprising:

[0056] a heat source for applying heat to a volume within the patient,

[0057] a probe body mounting the heat source thereon for allowinginvasive insertion of an end of the probe into the patient,

[0058] a supply duct on the probe body for a cooling fluid extendingfrom a supply to the end of the probe;

[0059] the probe body being arranged to provide an expansion zone ofreduced pressure at the end of the probe body so as to cause the coolingfluid to expand as a gas thus generating a cooling effect;

[0060] and a return duct on the probe body for return of the expandedgas from the end of the probe.

BRIEF DESCRIPTION OF THE DRAWINGS

[0061] One embodiment of the invention will now be described inconjunction with the accompanying drawings in which:

[0062]FIG. 1 is a schematic illustration of an apparatus for effectingMRI guided laser treatment according to the present invention.

[0063]FIG. 2 is a schematic illustration of the apparatus of FIG. 1 onan enlarged scale and showing the emission of laser energy into thebrain of a patient.

[0064]FIG. 3 is a side elevational view of the laser probe of theapparatus of FIG. 1.

[0065]FIG. 4 is an end elevational view of the laser probe of theapparatus of FIG. 1.

[0066]FIG. 5 is a cross sectional view of the laser probe and drivemotor therefor of the apparatus of FIG. 1.

[0067]FIG. 6 is an exploded view of the drive motor of the apparatus ofFIG. 1.

[0068]FIG. 7 is a schematic illustration of the shielding of theapparatus of FIG. 1.

[0069]FIG. 8 is a schematic illustration of the effect of the apparatuson a tumour or other lesion to be coagulated.

[0070]FIG. 9 is a longitudinal cross sectional view through analternative form of probe which provides a flow of cooling fluid to theend of the probe for cooling the surrounding tissue.

[0071]FIG. 10 is a cross sectional view along the lines 10-10 of FIG. 9.

[0072]FIG. 11 is a longitudinal cross sectional view through a furtheralternative form of probe which provides a flow of cooling fluid to theend of the probe for cooling the surrounding tissue.

[0073]FIG. 12 is a cross sectional view along the lines 12-12 of FIG.11.

[0074]FIG. 13 is a photograph of a cross section of a tissue samplewhich has been heated in three separate segments showing the absence ofheating outside the segments.

DETAILED DESCRIPTION

[0075] In FIG. 1 is shown schematically an apparatus for carrying outMRI controlled laser treatment. The apparatus comprises a magneticresonance imaging system including a magnet 10 provided within ashielded room 11. The magnet 10 can be of any suitable construction andmany different magnet arrangements are available from differentmanufacturers. The magnet includes field coils for generating variationsin the magnetic field which are not shown since these are well known toone skilled in the art together with a radio frequency antenna coilwhich receives signals from the sample in this case indicated as a humanpatient 13.

[0076] The patient 13 rests upon a patient support table 14 on which thepatient is supported and constrained against movement for the operativeprocedure. The fields of the magnet are controlled on an input controlline 15 and the output from the antenna coil is provided on an outputline 16 both of which communicate through a surgeon interface 17 to theconventional MRI control console 18. The MRI console and the magnet areshown only schematically since these are well known to one skilled inthe art and available from a number of different manufacturers.

[0077] The apparatus further includes a laser treatment system includingan optical fiber 20 which transmits heat energy in the form of lightfrom a laser 21 mounted outside the room 11. The fiber extends into theroom to a tip 21 (FIG. 2) at which the energy escapes into the relevantpart of the patient as discussed hereinafter. The position of the fiber20 within the patient and the orientation of the fiber is controlled bya drive motor 22 supported in fixed adjustable position on a stereotaxicframe 23. The motor communicates through a control line 24 to a devicecontroller 25. In general the device controller receives informationfrom the MRI console and from position detectors of the motor 22 so asto operate movement of the motor 22 and to operate a power output fromthe laser 21 so as to control the position and amount of heat energyapplied to the part within the body of the patient.

[0078] In FIG. 2 is shown on a larger scale the patient table 14 towhich is attached the stereotaxic frame 23 so that the frame is fixedrelative to the table and extends over the head 26 of the patient. Theframe is shown schematically and suitable details will be well known toone skilled in the art, but carries the motor 22 in a position on theframe by a bracket 27 of the motor. The position of the motor on theframe remains fixed during the procedure but can be adjusted in thearcuate direction 28 around the arch of the frame 23. The frame 23 canalso be adjusted forwardly and rearwardly on the table 14. The bracket27 also allows rotation of the motor about a point 30 within the frameso that the direction of the fiber projecting forwardly from the motorcan be changed relative to the frame.

[0079] The apparatus further includes a rigid cannula 31 which surroundsthe fiber 20 and which is arranged to allow sliding movement of thefiber longitudinally in the cannula and rotational movement within thecannula while generally holding the fiber in a direction axial of thecannula. The cannula is formed of a suitable rigid MRI compatiblematerial such as ceramic so that it is stiff and resistant to bendingand has sufficient strength to allow the surgeon to insert the cannulainto the required location within the body part of the patient.

[0080] In the arrangement as shown, the apparatus is arranged foroperating upon a tumour 32 within the brain 33 of the patient. Thesurgeon therefore creates an opening 34 in the skull of the patient anddirects the cannula 31, in the absence of the fiber 20, through theopening 34 to the front edge of the tumour 32.

[0081] The position of the tumour is determined in an initial set of MRIexperiments using conventional surgical and an analytical techniques todefine the boundaries, that is a closed surface within the volume of thebrain which constitutes the extremities of the tumour. The surgicalanalysis by which the surgeon determines exactly which portions of thematerial of the patient should be removed is not a part of thisinvention except to say that conventional surgical techniques areavailable to one skilled in the art to enable an analysis to be carriedout to define the closed surface.

[0082] The angle of insertion of the cannula is arranged so that, ofcourse, it avoids as far as possible areas of the patient which shouldnot be penetrated such as major blood vessels and also so that thecannula is directed so that, when it reaches the outside surface, itpoints toward a center of the tumour.

[0083] The optical fiber structure generally indicated at 20 in FIG. 3includes an actual glass fiber element 35 which has an inlet end (notshown) at the laser and a remote end 36. At the remote end is provided areflector or prism which directs the laser energy in a beam 37 to oneside of the end 36. Thus the beam 37 is directed substantially at rightangles to the length of the fiber and over a small angle around the axisof the fiber. The beam 37 forms a cone having a cone angle of the orderof 12 to 15 degrees. Such fibers are commercially available includingthe reflector or prism for directing the light at right angles to thelength of the fiber.

[0084] The fiber element itself as indicated at 35 is however encased inan enclosure to allow the fiber to be manipulated in the motor 22.Around the fiber is formed a sleeve 38 including a first end portion 39and a second longer portion 40. The end portion 39 encloses the end 36which is spaced from a tip 41 of the end portion. The end portionextends over the length of the order of 7 to 11 cm. The longer secondportion 38 is of the order of 48 to 77 cm in length and extends from aforward end 41 through to a rear end 42. The front portion 39 is formedof a rigid material such as glass. The longer rear portion 40 is formedof a stiff material which is less brittle than glass and yet maintainsbending and torsional stiffness of the fiber so that forces can beapplied to the sleeve portion 40 to move the tip 36 of the fiber to arequired position within the tumour. The second portion 40 is formed ofa material such as fiber reinforced plastics.

[0085] The two portions are bonded together to form an integralstructure of common or constant diameter selected as a sliding fitthrough the cannula. The rigid front portion has a length so that it canextend from the end of the cannula at the forward or closest edge of thetumour through to the rear edge of the tumour. An average tumour mighthave a diameter of the order of 0.5 to 5.0 cm so that the above lengthof the forward portion is sufficient to extend through the full diameterof the tumour while leaving a portion of the order of 1.25 cm within theend of the cannula. In this way the substantially rigid forward portionmaintains the forward portion of the fiber lying substantially directlyalong the axis of the cannula without any bending or twisting of theforward portion within the cannula. The longer second portion is notformed from glass since this would provide a complete structure which istoo brittle to allow the surgeon to insert the structure into thecannula without the danger of cracking or fracturing the structure underany bending loads. A less brittle material is therefore selected whichcan accommodate some bending loads caused by manual insertion of thestructure into the cannula and yet can communicate the forces fromlongitudinal and rotational movement as described herein after.

[0086] The sleeve portion 40 has attached to it a first polygonal ornon-circular section 44 and a second end stop section 45. Both of thedrive sections 44 and 45 are connected to the second portion so as tocommunicate driving action to the second portion. Thus the polygonalsection 44 is arranged to co-operate with a drive member which acts torotate the second portion and therefore the fiber along its full lengthabout an axis longitudinal of the fiber. The second end stop section 45is arranged to co-operate with a longitudinally movable drive elementwhich moves the second portion and therefore the fiber longitudinally.In this way the tip 36 can be moved from an initial position in which itprojects just beyond the outer end of the cannula outwardly into thebody of the tumour until the tip reaches the far end of the tumour. Inaddition the tip can be rotated around the axis of the fiber so that theheat energy can be applied at selected angles around the axis. Byselectively controlling the longitudinal movement and rotation of thetip, therefore, the heat energy can be applied throughout a cylindricalvolume extending from the end of the cannula along the axis of thecannula away from the end of the cannula. In addition by controlling theamount of heat energy applied at any longitudinal position and angularorientation, the heat energy can be caused to extend to required depthsaway from the axis of the cannula so as to effect heating of the bodypart of the patient over a selected volume with the intention ofmatching the volume of the tumour out to the predetermined closedsurface area defining the boundary of the tumour.

[0087] As shown in FIG. 4, the non-circular cross section of the driveportion 44 is rectangular with a height greater than the width. Howeverof course other non-circular shapes can be used provided that the crosssection is constant along the length of the drive portion and providedthat the drive portion can co-operate with a surrounding drive member toreceive rotational driving force therefrom. The end stop member 45 isgenerally cylindrical with a top segment 45A removed to assist theoperator in insertion of the fiber into the drive motor.

[0088] Turning now to FIGS. 5 and 6, the drive motor 22 is shown in moredetail for effecting a driving action on the fiber through the drivemembers 44 and 45 into the sleeve 38 for driving longitudinal androtational movement of the tip 36.

[0089] The drive motor comprises a housing 50 formed by an upper half 51and a lower half 52 both of semi-cylindrical shape with the two portionsengaged together to surround the drive elements with the fiber extendingaxially along a center of the housing. At the front 53 of the housing isprovided a boss defining a bore 54 within which the sleeve 38 forms asliding fit. This acts to guide the movement of the sleeve at theforward end of the housing.

[0090] Within the housing is provided a first annular mount 55 and asecond annular mount 56 spaced rearwardly from the first. Between thefirst annular mount and the front boss is provided a first encoder 57and behind the second annular mount 56 is provided a second encoder 58.

[0091] The first annular mount 55 mounts a first rotatable drive disk 59on bearings 60. The second annular mount carries a second drive disk 61on bearings 62. Each of the drive disks is of the same shape including agenerally flat disk portion with a cylindrical portion 63 on the rear ofthe disk and lying on a common axis with the disk portion. The bearingsare mounted between a cylindrical inner face of the annular portion 55,56 and an outside surface of the cylindrical portions 63. Each of thedisks is therefore mounted for rotation about the axis of the fiberalong the axis of the housing.

[0092] The disk 59 includes a central plug portion 64 which closes thecenter hole of the disk portion and projects into the cylindricalportion 63. The plug portion has a chamfered or frusto-conical lead insection 65 converging to a drive surface 66 surrounding the drive member44 and having a common cross sectional shape therewith. Thus the tipportion 41 of the sleeve 38 can slide along the axis of the housing andengage into the conical lead in section 65 so as to pass through thedrive surface or bore 66 until the drive member 44 engages into thesurface 66. In the position, rotation of the disk 59 drives rotation ofthe sleeve 38 and therefore of the fiber. As the drive portion 44 has aconstant cross section, it can slide through the drive surface 66forwardly and rearwardly.

[0093] The disk 61 includes a plug member 67 which engages into thecentral opening in the disk member 61. The plug 67 has an inner surface68 which defines a female screw thread for co-operating with a leadscrew 69. The lead screw 69 has an inner bore 70 surrounding the sleeve38 so that the sleeve 38 is free to rotate and move relative to the bore70. The lead screw 69 also passes through the cylindrical portion 63 ofthe disk 61. However rotation of the disk 61 acts to drive the leadscrew longitudinally of the axis of the housing and therefore of theaxis of the sleeve 38. A rear end 71 of the lead screw is attached to aclamping member 72. The clamping member 72 includes a first fixedportion 73 attached to the rear end 71 of the lead screw and a secondloose portion 74 which can be clamped into engaging the fixed portion soas to clamp the end stop members 45 in position within the clampingmember. The loose portion 74 is clamped in place by screws 75. The topsegment 45A of the end stop 45 engages into a receptacle 76 in the fixedportion 73 so as to orient the sleeve 38 relative to the lead screw.

[0094] The disks 59 and 61 are driven in a ratchetting action by drivemotors 77 and 78 respectively. In the preferred embodiment the drivemotors are provided by piezo-electric drive elements in which apiezo-electric crystal is caused to oscillate thus actuating areciprocating action which is used to drive by a ratchet process angularrotation of the respective disk.

[0095] The reciprocating action of the piezo-electric crystal 77 and 78is provided by two such motors 77 co-operating with the disk 59 and twomotors 78 co-operating with the disk 61. Each motor is carried on amounting bracket 77A, 78A which is suitably attached to the housing.

[0096] The end clamp 72 is generally rectangular in cross section andslides within a correspondingly rectangular cross section duct 72Awithin the housing. Thus the lead screw 69 is held against rotation andis driven axially by the rotation of the disk 61 while the fiber is freeto rotate relative to the lead screw.

[0097] In other alternative arrangements (not shown), the ratchettingaction can be effected by a longitudinally moveable cable driven fromthe device controller 25 outside the room 11. In a further alternativearrangement, the motor may comprise a hydraulic or pneumatic motor whichagain effects a ratchetting action by reciprocating movement of apneumatically or hydraulically driven prime mover.

[0098] Thus selected rotation of a respective one of the disks can beeffected by supplying suitable motive power to the respective motor.

[0099] The respective encoder 57, 58 detects the instantaneous positionof the disk and particularly the sleeve portion 63 of the disk whichprojects into the interior of the encoder. The sleeve portion thereforecarries a suitable elements which allows the encoder to detectaccurately the angular orientation of the respective disk. In this waythe position of the disks can be controlled by the device controller 25accurately moving the disk 59 to control the angular orientation of thefiber and accurately moving the disk 61 to control the longitudinalposition of the fiber. The longitudinal position is of course obtainedby moving the lead screw longitudinally which carries the end stop 45longitudinally. The movements are independent so that the fiber can berotated while held longitudinally stationary.

[0100] As the motor driving movement of the fiber is used while themagnet and the MRI system is in operation, it is essential that themotor and the associated control elements that are located within theroom 11 are compatible with the MRI system. For this purpose, the powersupply or control cable 24 and the motor must both be free fromferromagnetic components which would be responsive to the magneticfield. In addition it is necessary that the motor 22 and the cable 24are both properly shielded against interference with the small radiofrequency signals which must be detected for the MRI analysis to beeffective.

[0101] As shown in FIG. 7, therefore, the room 11 is surrounded by aconductor which prevents penetration of radio frequency interferenceinto the area within the room at the magnet. In addition the cable 24and the motor 22 are surrounded by a conductor 80 which extends throughan opening 81 in the conductor at the wall 11 through a cable port 82within the wall 83 of the enclosure so that the whole of the motor andthe cable are encased within the conductor 80 which is connected to theconductor within the wall. Thus the conductor 80 acts as a “worm hole”in the shielding thus retaining the motor 22 and the cable 24effectively external to the shielding at the periphery of the room. Theuse of a Piezo-electric crystal to drive disks is particularly suitableand provides particular compatibility with the MRI system but otherdrive systems can also be used as set forth previously.

[0102] In the method of operation, the patient is located on the patienttable and so to be restrained so that the head of the patient is heldfixed within the magnet to prevent motion artefacts. The MRI system isthen operated in conventional manner to generate an image of theportion, generally a tumour, to be excised. The surgeon alone or inconjunction with suitable software available to one skilled in the artthen analyses the images developed to locate the closed area surroundingthe volume of the tumour and defining the external perimeter of thetumour as indicated at FIG. 8 at 90. The surgeon also determines thebest route for directing the cannula to the tumour to avoid damagingintervening tissue and to provide a best course to the centre of thetumour which may be irregular in shape.

[0103] Having determined the course and direction of the cannula, theopening 34 is formed and the cannula inserted as previously described.

[0104] With the cannula in place, the motor is mounted on the frame andthe frame adjusted to locate the motor so that the fiber can be inserteddirectly along the length of the cannula. With the motor properlyaligned along the axis of the cannula, the fiber is inserted through thebore of the motor and into the cannula so as to extend through thecannula until the tip emerges just out of the outer end of the cannula.The distance of the motor from the cannula can be adjusted so that thetip just reaches the end of the cannula when the lead screw is fullyretracted and the end stop is located in place in the clamp 72.

[0105] With the motor and fiber thus assembled, the MRI system isarranged to carry out experiments which generate temperaturemeasurements in the boundary zone 90. The temperature is detected overthe full surface area of the boundary rather than simply at a number ofdiscrete locations. While the experiments to detect the temperature arecontinued, the fiber is moved longitudinally to commence operation at afirst position just inside the volume of the tumour. At a selectedangular orientation of the beam, pulses of radiation are emitted by thelaser and transmitted into the tumour through the beam 37. The pulsesare continued while the temperature in the boundary layer 90 isdetected. As the pulses supply heat energy into the volume of thetumour, the tumour is heated locally basically in the segment shapedzone defined by the beam but also heat is conducted out of the volume ofthe beam into the remainder of the tumour at a rate dependant upon thecharacteristics of the tumour itself. Heating at a localised areadefined by the beam is therefore continued until the heat at theboundary layer 90 is raised to the predetermined coagulation temperatureof the order of 55 to 65° C. Once the boundary layer reaches thistemperature, heating at that segment shaped zone within the disk isdiscontinued and the fiber is moved either longitudinally to anotherdisk or angularly to another segment or both to move to the next segmentshaped zone of the tumour to be heated. It is not necessary to predictthe required number of pulses in advance since the detection oftemperature at the boundary is done in real time and sufficientlyquickly to prevent overshoot. However, predictions can be made in somecircumstances in order to carry out the application of the heat energyas quickly as possible by applying high power initially and reducing thepower after a period of time.

[0106] It is of course desirable to effect heating as quickly aspossible so as to minimize the operation duration. For this purpose thenumber of pulses per second, or power of the heat source, may also bevaried based upon the above predication depending upon thecharacteristics of the tumour as detected in the initial analysis. Thusthe system may vary the energy pulse rate or power-time history of theheat source to modify the penetration depth of the heat induced lesionso that it can control the heating zone of an irregularly shaped lesion.

[0107] However the energy application rate cannot be so high that thetemperature rises too quickly so that over shooting of the desiredtemperature at the boundary occurs with the possibility of damage totissue outside the boundary. The rate of energy application is thereforeselected depending upon the size and consistency of the tumour to effectheating at a controlled rate in order to achieve the requiredtemperature at the boundary without the possibility of over shoot. Therate of heat application can also be varied in dependence upon thedistance of the boundary from the axis of the fiber. Thus the axis ofthe fiber is indicated at 91 in FIG. 8 and a first distance 92 of thebeam to the boundary is relatively short at the entry point of the fiberinto the tumour and increases to a second larger distance 93 toward thecenter of the tumour. In addition to pulses per second, it is alsopossible to adjust the power-time history of the laser energy tomaximize penetration into the lesion. That is to use high power firstfor a short period of time and then ramp the power down throughout theduration of the treatment at that particular location.

[0108] In some cases it is desirable to maintain the fiber stationary ata first selected longitudinal position and at a first selected angularorientation until the temperature at the boundary reaches the requiredtemperature. In this case the fiber is then rotated through an angleapproximately equal to the beam angle to commence heating at a secondangular orientation with the fiber being rotated to a next angularorientation only when heating at that second orientation is complete. Inthis way heating is effected at each position and then the fiber rotatedto a next orientation position until all angular orientations arecompleted.

[0109] After a first disk shaped portion of the tumour is thus heated,the fiber is moved longitudinally through a distance dependant upon thediameter of the tumour at that location and dependant upon the beamangle so as to ensure the next disk shaped volume of tumour heatedcontains all of the tumour structure without intervening localisedportions of the tumour which are not heated to the required temperature.Thus the fiber is moved longitudinally in steps which may vary indistance depending upon the diameter and structure of the tumour asdetermined by the initial analysis. However the total heating of thetumour is preferably determined by the temperature at the boundarywithout the necessity for analysis of the temperatures of the tumourinside the boundary or any calculations of temperature gradients withinthe tumour.

[0110] When the complete boundary of the tumour has been heated to thepredetermined coagulation temperature, the treatment is complete and theapparatus is disassembled for removal of the fiber and the cannula fromthe patient.

[0111] The system allows direct and accurate control of the heating bycontrolling the temperature at the surface area defined by the boundaryof the tumour so that the whole of the volume of the tumour is properlyheated to the required temperature without the danger of heating areasexternal to the tumour beyond the coagulation temperature.

[0112] In order to maximize the amount of heat energy which can beapplied through the fiber and thereby to effect treatment of largertumors, it is highly desirable to effect cooling of the tissueimmediately surrounding the end of the fiber so as to avoid overheatingthat portion of the tissue. Overheating beyond the coagulationtemperature is unacceptable since it will cause carbonization which willinhibit further transmission of the heat energy. Thus without thecooling it is generally necessary to limit the amount of heat energywhich is applied. As energy dissipates within the tissue, such alimitation in the rate of application of energy limits the size of thetumor to be treated since dissipation of energy prevents the outsideportions of the tumor from being heated to the required coagulationtemperature.

[0113] In FIGS. 9 and 10 is therefore shown a modified laser probe whichcan be used in replacement for the probe previously described, bearingin mind that it is of increased diameter and thus minor modifications tothe dimensions of the structure are necessary to accommodate themodified probe.

[0114] The modified probe 100 comprises a fiber 101 which extends from atip portion 102 including the light dispersion arrangement previouslydescribed to a suitable light source at an opposed end of the fiber aspreviously described. The probe further comprises a support tube 103 inthe form of a multi-lumen extruded plastics catheter for the fiber whichextends along the fiber from an end 104 of the tube just short of thetip 102 through to a position beyond the fiber drive system previouslydescribed. The tube 103 thus includes a cylindrical duct 104 extendingthrough the tube and there are also provided two further ducts 105 and106 parallel to the first duct and arranged within a cylindrical outersurface 107 of the tube.

[0115] The supporting tube 103 has at its end opposite the outer end 104a coupling 108 which is molded onto the end 109 and connects individualsupply tubes 110, 111 and 112 each connected to a respective one of theducts 104, 105 and 106.

[0116] Multi-lumen catheters of this type is commercially available andcan be extruded from suitable material to provide the requireddimensions and physical characteristics. Thus the duct 104 isdimensioned to closely receive the outside diameter of the fiber so thatthe fiber can be fed through the duct tube 110 into the duct 104 and canslide through the support tube until the tip 102 is exposed at the end104.

[0117] While tubing may be available which provides the requireddimensions and rigidity, in many cases, the tubing is however flexibleso that it bends side to side and also will torsionally twist. Thesupport tube is therefore mounted within an optional stiffening tube orsleeve 114 which extends from an end 115 remote from the tip 102 to asecond end 106 adjacent to the tip 102. The end 116 is however spacedrearwardly from the end 104 of the tubing 103 which in turn is spacedfrom the tip 102. The distance from the end 106 to the tip 102 isarranged to be less than a length of the order of 1 inch. The stiffeningtube 114 is formed of a suitable stiff material which isnon-ferro-magnetic so that it is MRI compatible. The support tube 103 isbonded within the stiffening tube 114 so that it cannot rotate withinthe stiffening tube and cannot move side to side within the stiffeningtube. The stiffening tube is preferably manufactured from titanium,ceramic or other material which can accommodate the magnetic fields ofMRI. Titanium generates an artifact within the MRI image. For thisreason the end 116 is spaced as far as possible from the tip 102 so thatthe artifact is removed from the tip to allow proper imagining of thetissues.

[0118] At the end 116 of the stiffening tube 114 is provided a capsule120 in the form of a sleeve 121 and domed or pointed end 122. The sleevesurrounds the end 116 of the stiffening tube and is bonded thereto so asto provide a sealed enclosure around the exposed part of the tube 103.The capsule 120 is formed of quartz crystal so as to be transparent toallow the escape of the disbursed light energy from the tip 102. Thedistance of the end of the stiffening tube from the tip is arranged suchthat the required length of the capsule does not exceed what can bereasonably manufactured in the transparent material required.

[0119] The tube 111 is connected to a supply 125 of a cooling fluid andthe tube 112 is connected to a return collection 126 for the coolingfluid. Thus the cooling fluid is pumped through the duct 105 and escapesfrom the end 104 of the tube 103 into the capsule and then is returnedthrough the duct 106. The cooling fluid can simply be liquid nitrogenwhich is allowed to expand to nitrogen gas at cryogenic temperatureswhich is then pumped under the pressure in the gas through the duct 105and returns through the duct 106 where it can be simply released toatmosphere at the return 126.

[0120] In an alternative arrangement the supply 125 and the return 126form parts of a refrigeration cycle where a suitable coolant iscompressed and condensed at the supply end and is evaporated at thecooling zone at the capsule 120 so as to transfer heat from the tissuesurrounding the capsule 120 to the cooling section at the supply end.

[0121] The arrangement set forth above allows the effective supply ofthe cooling fluid in gaseous or liquid form through the ducts 105 and106 and also effectively supports the fiber 101 so that it is heldagainst side to side or rotational movement relative to the stiffeningtube 114. The location of the tip 102 of the fiber is therefore closelycontrolled relative to the stiffening tube and the stiffening tube isdriven by couplings 130 and 131 shown schematically in FIG. 9 but of thetype described above driven by reciprocating motor arrangements as setforth hereinbefore.

[0122] In FIGS. 11 and 12 is shown the tip section of an alternativeprobe in which cooling of the tip section is effected using expansion ofa gas into an expansion zone. The tip only is shown as the remainder ofthe probe and its movement are substantially as previously described.

[0123] Thus the probe comprises a rigid extruded tube 200 of a suitablematerial for example titanium which is compatible with MRI(non-ferromagnetic) and suitable for invasive medical treatment. Afurther smaller cooling fluid supply tube 202 is also separately formedby extrusion and is attached by adhesive to the inside surface of theouter tube. An optical fiber 204 is also attached by adhesive to theinside surface the outer tube so that the fiber is preferablydiametrically opposed to the tube 202.

[0124] The tube 202 is swaged at its end as indicated at 205, whichprojects beyond the end of the tube 201, to form a neck section ofreduced diameter at the immediate end of the tube 202. Thus inmanufacture the extruded tube 201 is cut to length so as to define a tipend 207 at which the outer tube terminates in a radial plane. At the tipend beyond the radial plane, the outer of the inner tube 202 is swagedby a suitable tool so as to form the neck section 205 having an internaldiameter of the order of 0.003 to 0.005 inch.

[0125] The fiber 204 is attached to the tube 201 so that a tip portion208 of the fiber 204 projects beyond the end 207 to a chamfered end face209 of the fiber which is cut at 45° to define a reflective end plane ofthe fiber.

[0126] The end 207 is covered and encased by a molded quartz end cap 210which includes a sleeve portion 211 closely surrounding the last part ofthe tube 200 and extending beyond the end 207 to an end face 212 whichcloses the capsule. The end face 212 is tapered to define a nose 213which allows the insertion of the probe to a required location aspreviously described. The end of the tube 201 may be reduced in diameterso that the capsule has an outer diameter matching that of the mainportion of the tube. However in the arrangement shown the capsule isformed on the outer surface so that its outer diameter is larger thanthat of the tube and its inner diameter is equal to the outer diameterof the tube.

[0127] A thermocouple 214 is attached to the inside surface of the outertube 200 at the end 207 and includes connecting wires 215 which extendfrom the thermocouple to the control unit schematically indicated at226. Thus the thermocouple provides a sensor to generate an indicationof the temperature at the end 207 within the quartz capsule. The quartzcapsule is welded to or bonded to the outer surface of the tube asindicated at 215 so as to form a closed expansion chamber within thequartz capsule beyond the end 207. The inner surface 216 of the quartzcapsule is of the same diameter as the outer surface of the tube 200 sothat the expansion chamber beyond the end of the tube 200 has the sameexterior dimension as the tube 200.

[0128] The quartz capsule is transparent so as to allow the reflectedbeam of the laser light from the end face 209 of the fiber to escapethrough the transparent capsule in the limited angular directionsubstantially at right angles to the longitudinal axis of the fiber andwithin the axial plane defined by that longitudinal axis.

[0129] The tube 202 is connected at its end opposite to the tip to afluid supply 219 which forms a pressurized supply of a suitable coolingfluid such as carbon dioxide or nitrous oxide. The fluid supply 219 iscontrolled by the control unit 216 to generate a predetermined pressurewithin the fluid supply to the tube 202 which can be varied so as tovary the flow rate of the fluid through the neck 205. The fluid issupplied at normal or room temperature without cooling. The fluid isnormally a gas at this pressure and temperature but fluids which areliquid can also be used provided that they form a gas at the pressureswithin the expansion chamber and thus go through an adiabatic gasexpansion through the restricted orifice into the expansion chamber toprovide the cooling effect.

[0130] Thus the restricted orifice has a cross-sectional area very muchless than that of the expansion chamber and the return duct provided bythe inside of the tube 201. The items that reduce the effective crosssectional area of the return tube 201 are the optical fibre, the supplytube, two thermocouple wires, the shrink tube that fixes thethermocouple wires to the optical fibre and the adhesives used to bondthe items into place (at the inlet of the discharge duct). Without thearea of the adhesives included in the calculation, the exhaust duct areais about 300 times larger than a delivery orifice diameter of 0.004″(the target size). When considering the area occupied by the adhesives,the exhaust duct inlet area would be approximately 200 to 250 timeslarger than the 0.004″ diameter orifice. Considering the manufacturingtolerance range of the supply tube orifice diameter alone, the exhaustduct area could be anywhere between 190 to 540 times larger than theorifice area (without considering the area occupied by adhesives). It isour estimation that a 200/1 gas expansion will be required to achieveappropriate cooling.

[0131] This allows the gas as it passes into the expansion chamberbeyond the end 205 to expand as a gas thus cooling the quartz capsuleand the interior thereof at the expansion chamber to a temperature inthe range minus 20° C. to zero ° C. This range has been found to besuitable to provide the required level of cooling to the surface of thequartz capsule so as to extract heat from the surrounding tissue at arequired rate. Variations in the temperature in the above range can beachieved by varying the pressure from the supply 219 so that in oneexample the pressure would be of the order of 700 to 850 psi at a flowrate of the order of 5 liters per min.

[0132] The tube 202 has an outside diameter of the order of 0.014 inchOD, the tube 203 has a diameter of the order of 0.079 inch. Thus adischarge duct for the gas from the expansion chamber is defined by theinside surface of the tube 200 having a flow area which is defined bythe area of the tube 200 minus the area taken up by the tube 202 and thefiber 207. This allows discharge of the gas from the expansion chamberdefined within the quartz capsule at a pressure of the order of 50 psiso that the gas can be simply discharged to atmosphere if inert or canbe discharged to an extraction system or can be collected for coolingand returned to the fluid supply 219 if economically desirable. Tipcooling is necessary for optimum tissue penetration of the laser orheating energy, reduction of tissue charring and definition of the shapeof the coagulated zone. The gas expansion used in the present inventionprovides an arrangement which is suitable for higher power densitiesrequired in this device to accommodate the energy supplied by the laserheating system.

[0133] The tip 208 of the fiber 204 is accurately located within theexpansion zone since it is maintained in fixed position within thequartz capsule by its attachment to the inside surface of the outertube. The fiber is located forwardly of the end 207 sufficiently thatthe MRI artifact generated by the end 207 is sufficiently removed fromthe plane of the fiber end to avoid difficulties in monitoring thetemperature within the plane of the fiber end. The outlet orifice of thetube 202 is also located forwardly of the end 207 so as to be locatedwith the cooling effect generated thereby at the plane of the fiber end.

[0134] The end face 209 is located within the expansion chamber 216 sothat it is surrounded by the gas with no liquid within the expansionchamber. Thus in practice there is no condensate on the end face 209 norany other liquid materials within the expansion chamber which wouldotherwise interfere with the reflective characteristics of the end face209.

[0135] The end face 209 is coated with a reflective coating such as adual dielectric film. This provides a reflection at two required wavelengths of the laser light which are used as a visible guide beam and asthe heat energy source such as He—Ne and Nd:YAG respectively. Analternative coating is gold which can alone provide the reflections atthe two wavelengths.

[0136] The arrangement of the present invention provides excellent MRIcompatibility both for anatomic imaging as well as MR thermal profiling.

[0137] In operation, the temperature within the expansion zone ismonitored by the sensor 214 so as to maintain that temperature at apredetermined temperature level in relation to the amount of heat energysupplied through the fiber 204. Thus the pressure within the fluidsupply is varied to maintain the temperature at that predetermined setlevel during the hyperthermic process.

[0138] As described previously, the probe is moved to an axial locationwithin the volume to be treated and the probe is rotated in steps so asto turn the heating zone generated by the beam B into each of aplurality of segments within the disk or radial plane surrounding theend face 209. Within each segment of the radial plane, heat energy issupplied by the beam B which is transmitted through the quartz capsuleinto the tissue at that segment. The heat energy is dissipated from thatsegment both by reflection of the light energy into adjacent tissue andby conduction of heat from the heated tissue to surrounding tissue.

[0139] The surface of the capsule is cooled to a temperature so that itacts to extract heat from the surrounding tissue at a rate approximatelyequal to the dissipation or transfer of heat from the segment into thesurrounding tissue. Thus the net result of the heating effect is thatthe segment alone is heated and surrounding tissue not in the segmentrequired to be heated is maintained without any effective heatingthereon, that is no heating to a temperature which causes coagulation orwhich could otherwise interfere with the transmission of heat when itcomes time to heat that tissue in another of the segments. In this waywhen a first segment is heated to the required hyperthermic temperaturethroughout its extent from the probe to the peripheral surface of thevolume, the remaining tissues in the areas surrounding the probe areeffectively unheated so that no charring or coagulation has occurredwhich would otherwise prevent dissipation of heat and in extreme casescompletely prevent penetration of the beam B.

[0140] Thus when each segment in turn has been heated, the probe can berotated to the next segment or to another segment within the same radialplane and further heating can be effected of that segment only.

[0141] In practice in one example, the laser energy can be of the orderof 12 to 15 watts penetrating into a segment having an angle of theorder of 60 to 80 degrees to a depth of the order of 1.5 cms. In orderto achieve this penetration without causing heating to the remainingportions of the tissue not in the segment, cooling of the outside of thecapsule to a temperature of the order of minus 5 degrees C. is required.

[0142] In FIG. 13 is shown an actual example of a cross-section oftissue which has been heated in three separate segments marked assectors 1, 2 and 3. The central dark area is where the probe was locatedbefore it was removed to allow the cross-sectional slice to be taken.The darker area which forms approximately 100 degrees opposite sector 2indicates that no heating has been applied to that area. The lightercolor in the sectors 1, 2 and 3 indicates coagulation of the tissue.Similarly it will be noted that the tissue is of the darker color (notheated) in the smaller areas between sectors 2 and 3 and between sectors1 and 2. Thus the cooling effect of the present invention achieves theeffect required of limiting or prevention heating to the areas outsidethe selected segments.

[0143] The tube 200 is in the example shown above of a rigid structurefor insertion in a straight line as previously described into a specificlocation. The use of a rigid material such as titanium for the outertube avoids the necessity for the cannula previously described andallows the alignment of the probe in its mounting and drive arrangementas previously described to the required location in the patient withoutpreviously setting up a cannula. However other arrangements can beprovided in which the tube 200 is formed of a fully or partial flexiblematerial allowing the tube 200 to bend so as to allow insertion alongsuitable passageways such as veins or arteries within the patient byusing guiding systems well known to one skilled in the art.

[0144] Since various modifications can be made in my invention as hereinabove described, and many apparently widely different embodiments ofsame made within the spirit and scope of the claims without departingfrom such spirit and scope, it is intended that all matter contained inthe accompanying specification shall be interpreted as illustrative onlyand not in a limiting sense.

1. A method for effecting treatment in a patient comprising: identifyinga volume in the patient the whole of which volume is to be heated to arequired temperature, the volume being defined by a peripheral surfaceof the volume; providing a heat source and applying heat to the volumewithin the patient by; providing the heat source on an invasive probehaving a longitudinal axis and an end; inserting the end of the probeinto the volume; arranging the probe to cause directing of heat from theend in a direction at an angle to the longitudinal axis such that aheating effect of the probe lies in a disk surrounding the axis;arranging the direction of the heat so as to define a heating zone whichforms a limited angular orientation of heating within the disk suchthat, as the probe is rotated, the probe causes heating of differentangular segments of the volume within the disk; with the probe at afixed axial position, rotating the probe about the axis so that theheating zone lies in a selected segment; wherein the application of heatby the probe to the selected segment causes heat to be transferred fromthe segment into parts of the volume outside the segment surrounding theend of the probe; and applying cooling to the end of the probe so as toextract heat from the parts surrounding the probe by conduction of heattherefrom.
 2. The method according to claim 1 including arranging theamount of cooling to the probe relative to the heating such that theparts of the volume surrounding the end of the probe are cooledsufficiently to cause a net heating effect by which substantially onlythe segment of the heating zone is heated to the required temperatureand the parts outside the segment are not heated to the requiredtemperature.
 3. The method according to claim 2 wherein the cooling isarranged to maintain the parts outside the segment below a temperaturesufficient to cause coagulation of the tissues therein.
 4. The methodaccording to claim 1 including moving the end of the probe axiallywithin the volume so as to move the disk of the heating effect axiallywithin the volume from a first disk position to second disk position. 5.The method according to claim 1 including the steps of: operating anon-invasive detection system to generate a series of output signalsover a period of time representative of temperature in the patient asthe temperature of the patient changes during that time; using theoutput signals to monitor at least one temperature of the volume as thetemperature changes over the period of time; wherein the temperature atthe peripheral surface of the volume is monitored and a measure of thetemperature of the segment at the peripheral surface of the volume isused as the determining factor as to when to halt heating by the probeto the segment.
 6. The method according to claim 1 wherein the heatsource comprises a laser, an optical fiber for communicating light fromthe laser and a light directing element at an end of the fiber fordirecting the light from the laser to the predetermined directionrelative to the fiber and for forming the limited angular orientationwithin the disk.
 7. The method according to claim 1 wherein the end ofthe probe is cooled by: providing on the probe a supply duct for acooling fluid extending from a supply to the end of the probe; providingan expansion zone of reduced pressure at the end of the probe so as tocause the cooling fluid to expand as a gas thus generating a coolingeffect; and providing on the probe a return duct for return of theexpanded gas from the end of the probe.
 8. The method according to claim7 wherein the temperature of the probe is cooled to a temperature in therange of about zero to about minus 20 degrees Celsius.
 9. The methodaccording to claim 8 wherein the return duct is of largercross-sectional area than the supply duct by a factor of the order of200 to 250 times.
 10. The method according to claim 1 wherein the powerof the heat source is reduced during heating of each segment from aninitial high value to a lower value.
 11. The method according to claim 7wherein the probe comprises an outer tube, wherein the supply duct isarranged inside the outer tube and wherein the return duct is defined byan inside surface of the outer tube.
 12. The method according to claim11 wherein the supply duct is attached to an inside surface of the outertube.
 13. The method according to claim 11 wherein the probe includes aheat energy supply conduit for transporting the heat energy from asupply to the end of the probe and wherein the heat energy supplyconduit is attached to the inside surface of the outer tube.
 14. Themethod according to claim 7 wherein the cooling fluid is a gas which isexpanded through a restricting orifice.
 15. The method according toclaim 14 wherein the supply duct comprises a tube and the restrictingorifice is formed by a reduced necking of the tube at an end thereof atthe expansion zone.
 16. The method according to claim 15 wherein theprobe includes an outer tube and the supply duct is mounted within theouter tube with the end thereof including the necking extending beyondan end of the outer tube.
 17. The method according to claim 9 whereinthe heat source comprises a laser, an optical fiber for communicatinglight from the laser, and a light directing element at an end of thefiber, wherein the light directing element comprises a chamfered end ofthe fiber and wherein the chamfered end is located in the gas in theexpansion zone.
 18. The method according to claim 17 wherein thechamfered end is arranged at 45 degrees.
 19. The method according toclaim 17 wherein the chamfered end carries a coating arranged to reflectlight at two different wavelengths.
 20. The method according to claim 1wherein there is provided a temperature sensor at the end of the probe.21. The method according to claim 12 wherein the probe comprises anouter tube and wherein there is provided a temperature sensor mounted onthe inside surface of the tube at the end of the probe.
 22. The methodaccording to claim 7 wherein the temperature at the end of the probe iscontrolled by varying the pressure in the fluid as supplied through thesupply duct.
 23. A method for effecting treatment in a patientcomprising: identifying a volume in the patient to be heated to arequired temperature; providing a heat source for applying heat to thevolume within the patient, providing a probe mounting the heat sourceallowing invasive insertion of an end of the probe into the patient,providing a position control system for moving the end of the probe to arequired position within the patient; inserting the end of the probeinto the volume; providing on the probe a supply duct for a coolingfluid extending from a supply to the end of the probe; providing anexpansion zone of reduced pressure at the end of the probe so as tocause the cooling fluid to expand as a gas thus generating a coolingeffect; and providing on the probe a return duct for return of theexpanded gas from the end of the probe.
 24. The method according toclaim 23 wherein the temperature of the probe is cooled to a temperaturein the range of about zero to about minus 20 degrees Celsius.
 25. Themethod according to claim 23 wherein the return duct is of largercross-sectional area than the supply duct.
 26. The method according toclaim 25 wherein the return duct is of the order of 200 to 250 timeslarger than the supply duct.
 27. The method according to claim 23wherein the probe comprises an outer tube, wherein the supply duct isarranged inside the outer tube and wherein the return duct is defined byan inside surface of the outer tube.
 28. The method according to claim27 wherein the supply duct is attached to an inside surface of the outertube.
 29. The method according to claim 27 wherein the probe includes aheat energy supply conduit for transporting the heat energy from asupply to the end of the probe and wherein the heat energy supplyconduit is attached to the inside surface of the outer tube.
 30. Themethod according to claim 23 wherein the cooling fluid is a gas which isexpanded through a restricting orifice.
 31. The method according toclaim 30 wherein the supply duct comprises a tube and the restrictingorifice is formed by a reduced necking of the tube at an end thereof atthe expansion zone.
 32. The method according to claim 31 wherein theprobe includes an outer tube and the supply duct is mounted within theouter tube with the end thereof including the necking extending beyondan end of the outer tube.
 33. The method according to claim 23 whereinthe heat source comprises a laser, an optical fiber for communicatinglight from the laser, and a light directing element at an end of thefiber, wherein the light directing element comprises a chamfered end ofthe fiber and wherein the chamfered end is located in the gas in theexpansion zone.
 34. The method according to claim 33 wherein thechamfered end is arranged at 45 degrees.
 35. The method according toclaim 33 wherein the chamfered end carries a coating arranged to reflectlight at two different wavelengths.
 36. The method according to claim 23wherein there is provided a temperature sensor at the end of the probe.37. The method according to claim 23 wherein the probe comprises anouter tube and wherein there is provided a temperature sensor mounted onthe inside surface of the outer tube at the end of the probe.
 38. Themethod according to claim 23 wherein the temperature at the end of theprobe is controlled by varying the pressure in the cooling fluid assupplied through the supply duct.
 39. The method according to claim 23wherein the heat source comprises a laser and an optical fiber forcommunicating light from the laser to the end of the probe, and whereinthe probe includes an outer tube and a transparent capsule enclosing anend of the outer tube with the fiber extending to a position beyond theend of the tube into the capsule.
 40. A probe for use in effectingtreatment in a patient comprising: a heat source for applying heat to avolume within the patient, a probe body mounting the heat source thereonfor allowing invasive insertion of an end of the probe into the patient,a supply duct on the probe body for a cooling fluid extending from asupply to the end of the probe; the probe body being arranged to providean expansion zone of reduced pressure at the end of the probe body so asto cause the cooling fluid to expand as a gas thus generating a coolingeffect; and a return duct on the probe body for return of the expandedgas from the end of the probe.
 41. The probe according to claim 40wherein the temperature of the probe is cooled to a temperature in therange of about zero to about minus 20 degrees Celsius.
 42. The probeaccording to claim 40 wherein the return duct is of largercross-sectional area than the supply duct.
 43. The probe according toclaim 42 wherein the return duct is of the order of 200 to 250 timeslarger than the supply duct.
 44. The probe according to claim 40 whereinthe probe body comprises an outer tube, wherein the supply duct isarranged inside the outer tube and wherein the return duct is defined byan inside surface of the outer tube.
 45. The probe according to claim 44wherein the supply duct is attached to an inside surface of the outertube.
 46. The probe according to claim 44 wherein the outer tubeincludes a heat energy supply conduit for transporting the heat energyfrom a supply to the end of the probe and wherein the heat energy supplyconduit is attached to the inside surface of the outer tube.
 47. Theprobe according to claim 40 wherein the cooling fluid is a gas which isexpanded through a restricting orifice.
 48. The probe according to claim47 wherein the supply duct comprises a supply tube and the restrictingorifice is formed by a reduced necking of the supply tube at an endthereof at the expansion zone.
 49. The probe according to claim 40wherein the probe body comprises an outer tube and the supply duct ismounted within the outer tube with the end thereof including the neckingextending beyond an end of the outer tube.
 50. The probe according toclaim 40 wherein the heat source comprises a laser, an optical fiber forcommunicating light from the laser, and a light directing element at anend of the fiber, wherein the light directing element comprises achamfered end of the fiber and wherein the chamfered end is located inthe gas in the expansion zone.
 51. The probe according to claim 50wherein the chamfered end is arranged at 45 degrees.
 52. The probeaccording to claim 50 wherein the chamfered end carries a coatingarranged to reflect light at two different wavelengths.
 54. The probeaccording to claim 40 wherein there is provided a temperature sensor atthe end of the probe.
 55. The probe according to claim 40 wherein theprobe body comprises an outer tube and there is provided a temperaturesensor mounted on the inside surface of the outer tube at the end of theprobe.
 56. The probe according to claim 40 wherein the temperature atthe end of the probe is controlled by varying the pressure in thecooling fluid as supplied through the supply duct.
 57. The probeaccording to claim 40 wherein the heat source comprises a laser and anoptical fiber for communicating light from the laser to the end of theprobe, and wherein the probe includes an outer tube and a transparentcapsule enclosing an end of the outer tube with the fiber extending to aposition beyond the end of the outer tube into the capsule.